The invention relates to a method for centerless cylindrical grinding, for which the rotationally symmetrical workpiece is located between the grinding disk, the regulating wheel and the support guide during the grinding process and for which the distance between the grinding disk and the regulating wheel as well as the height setting of the support guide can be adjusted selectively during the grinding process.
A method of this type, which is frequently also referred to in practice as “centerless method”, is known, for example, from the DE 32 02 341 A1. In this publication, it is stated that the position of the workpiece between the grinding disk, the regulating wheel and the support guide, optimum for the grinding process and required for an optimum grinding result, cannot be adjusted easily. Since the regulating wheel must also bring about the advance of the workpiece, it assumes a position that is tilted slightly out of the horizontal. The workpiece lies in a manner, which cannot be defined precisely, between the regulating wheel and the support guide; in this position, it is pressed in by the grinding disk. It is advantageous here for the support guide to be also tilted slightly out of the horizontal. The determining process parameters for preparing the machine for the grinding process are the axial distance between the grinding disk and the regulating wheel, as well as the height adjustment of the support guide. For each diameter of a workpiece, there is a most suitable axial distance from the grinding disk and the regulating wheel and, for this, the most suitable height adjustment of the support guide must be found once again. The matching of these process parameters requires much experience.
So that the cumbersome adjustment by hand, optionally by trial and error and by test runs, will not have to be carried out whenever the machine is changed over to a new type of workpiece, it has already been proposed in DE 32 02 341 A1 a particular height adjustment of the support guide be assigned to each axial distance between the grinding disk and the regulating wheel. For this purpose, the regulating wheel is mounted in the usual manner in a headstock carriage, which can be screwed down in the direction of the grinding disk. When the grinding disk and the regulating wheel are adjusted to a particular axial distance corresponding to a particular diameter of the workpiece, a forced mechanical coupling between the headstock carriage and the support guide causes a particular value for the height setting of the support guide to come about at the same time. According to the proposal of the DE 32 02 341 A1, said adjustment can also be made during the grinding process when the contacting force of the grinding disk must be corrected. As a result, for each approach of the regulating wheel to the grinding disk, the support guide is raised by a certain amount at the same time.
However, the quite difficult processing position of the workpiece, once set, changes very rapidly when the external diameter of the workpiece decreases during the grinding. This is the case particularly when the diameter changes greatly, as it does very rapidly with the CBN grinding disks, the use of which is customary at the present time. However, if the optimum operating position of the workpiece between the grinding disk and the regulating wheel is disturbed, the grinding result also deteriorates; a labile position of the workpiece can also come about. In every case, the danger exists that the workpiece will be ground out of round. This deficiency cannot be eliminated with the known grinding device. Admittedly, by a selective adjustment by hand, the known grinding device permits some change in the distance between the grinding disk and the regulating wheel in a forced coupling with the height adjustment of the support guide. However, the possibilities of the device are no longer adequate to meet the present-day requirements for grinding accuracy in mass production.
It is therefore an object of the invention to provide a method for the centerless cylindrical grinding of the type named above, for which a position of the workpiece between the grinding disk, the regulating wheel and the support guide, required for an optimum grinding result, is ensured even in material that has been abraded heavily during the whole of the grinding process.